Process control systems, like those used in chemical, petroleum or other processes, typically include one or more centralized or decentralized process controllers communicatively coupled to at least one host or operator workstation and to one or more process control and instrumentation devices such as, for example, field devices, via analog, digital or combined analog/digital buses. Field devices, which may be, for example, valves, valve positioners, switches, transmitters, and sensors (e.g., temperature, pressure, and flow rate sensors), are located within the process plant environment, and perform functions within the process such as opening or closing valves, measuring process parameters, increasing or decreasing fluid flow, etc. Smart field devices such as field devices conforming to the HART®. protocol may also perform control calculations, alarming functions, and other control functions commonly implemented within the process controller.
Information from the field devices and the process controllers is typically made available to one or more other hardware devices such as, for example, operator workstations, maintenance workstations, personal computers, handheld devices, data historians, report generators, centralized databases, etc. to enable an operator or a maintenance person to perform desired functions with respect to the process such as, for example, changing settings of the process control routine, modifying the operation of the control modules within the process controllers or the smart field devices, viewing the current state of the process or of particular devices within the process plant, viewing alarms generated by field devices and process controllers, simulating the operation of the process for the purpose of training personnel or testing the process control software, diagnosing problems or hardware failures within the process plant, etc.
A process control system also typically includes various safety stations, e.g., safety showers, eye wash stations, located throughout the process plant to be used by workers in emergency situations. Operators of the process control system want to know when an event occurred, such as when a safety station is being used, so that a monitoring system is aware of the event. Operators also want to know about when an event occurred so that the monitoring system will continuously broadcast to a workstation that the event occurred, even when the safety station is reset to its original state, e.g., when the safety station is not being used.
One prior solution has used two devices to accomplish these objectives. More specifically, a first instrument has been secured to the safety station and used to perform a mechanical switch state diagnostic and latch if a detected activation of the one or more parts of the safety station occurs, e.g., the shower was turned on. A second instrument has also been secured to the safety station adjacent to the first instrument and reads the switch states of the first instrument. The second instrument, such as a wireless transmitter, then wirelessly broadcasts or transmits the first instrument switch states to a base station of the process control system. In this case, the mechanical latch of the first instrument must be reset by someone going out to the safety station and physically resetting the mechanical switch. In the event that the target operating device is a safety shower station, for example, the two instruments make sure someone is deployed to the scene to determine if anyone is injured, for example.